This invention relates to methods and apparatus for intelligent admixture and delivery of intravenous drugs and for tracking and pre-delivery and post-delivery verification and recording of drug dosages however administered to patients.
Although physicians, pharmacists, nurses, care givers and other health-care providers strive for error-free patient care, because of the complexity of modern medicine and the trend to minimize costs of delivery resulting in fewer and lower paid nurses, pharmacists, technicians and hospital employees, they frequently fall short of the mark. Indeed, the frequency of injuries from improperly formulated or delivered medication, (sometimes referred to as "adverse drug events") is rapidly increasing. Reduction of such injuries is an urgent need in light of the following statistic: researchers estimate that 180,000 people die in the U.S. annually from adverse drug events. That number of deaths is the equivalent of 3 jumbo jet crashes every 2 days. The severity of the problem is compounded by a general lack of awareness, amongst both clinicians and the general public, that a problem even exists. L. Leape, Error in Medicine Journal of the American Medical Association, Dec. 21, 1994, Vol. 272 No. 23, p. 1851.
Many of these adverse drug events result from errors in administering intravenous (IV) therapy. During any type of extensive hospitalization, a patient typically will receive some form of intravenous therapy because it is a fast and efficient route for the delivery of needed fluids and medications to a patient. The IV thus serves as the preferred transport vehicle for the intermittent delivery of a drug.
There are at least six basic classes of IV drugs: total parenteral nutrition (TPN); biotechnology (growth hormone for example); pain medication; continuous critical care medications; chemotherapy; and intermittents. Intermittent IV drugs are typically delivered in 4-6 doses spread out over a given period, such as a day, although other dosing intervals can be encountered.
Intermittent IV drugs can include, but are not limited to, antibiotics, antiemetics, H2 antagonists, steroids, and diuretics. IV drugs are typically prepared by the pharmacy or the manufacturer. Intermittent IV drugs represent one of the largest segments of medications delivered in a hospital.
For ease of use, manufacturers of intermittent IV drugs typically package the drugs into vials such as single-dose vials, multiple-dose vials and custom-dose vials. A single-dose vial is defined as a vial whose entire contents is acceptable or intended for use as a single dose to a patient. A multiple dose-vial is defined as a vial containing several doses of a drug. A custom dose vial is defined as a vial containing an amount of drug that is not prepackaged in a single or multiple dose "unit of use" configuration. The custom-dose vial can be used where a patient requires more or less than the contents of a single vial. Custom dosing can dictated by factors such as, for example, the patient's body weight, the patient's body surface area, lab results, and other factors.
Although clinicians may administer intermittent IV drugs quite often, the single- or multiple-dose vial configuration is typically not suitable for immediate intravenous delivery. This is because such drugs are normally packaged in a powdered, lyophilized or concentrated liquid form. Therefore, these drugs require conversion into a form more suitable for intravenous delivery. This conversion of intermittent IV drugs into a form suitable for intravenous delivery is known as the IV admixture process or simply admixture.
The admixture process normally includes a reconstitution step (if the medication is powdered or lyophilized, for example) and a dilution step. A pharmacist or technician ordinarily performs the admixture process after receipt of the prescription. This procedure is labor intensive and costly as well as fraught with potential error. Cohen M R, Davis N M. Medication Errors: Causes and Prevention, 1981. Schneider P J, Gift M G. Cost of medication-related problems at a university hospital. Am J Health-Syst Pharm. 1995; 52:2415-18. Belkin, Who's to Blame? It's the Wrong Question. N.Y. Times Magazine 1997, p 28-
Reconstitution, in the case of a lyophilized or powdered drug, involves the pharmacist or technician injecting a small amount of sterile water or other agent into the drug vial and agitating the vial to thoroughly dissolve the drug. Repetition of this procedure under aseptic conditions is difficult. Additionally, constant exposure of the technician to drugs, many of which are toxic in concentrated form, represents a hazard to the technician's health.
After reconstitution, a few of these drugs are now properly prepared for intravenous delivery. However, many drugs, after reconstitution, are too highly concentrated for immediate intravenous delivery. Such a concentrated solution could irritate or injure sensitive venous tissue. Thus, for most drugs, whether reconstituted or already available in concentrated liquid form, they must typically be diluted to prevent vein or tissue injury.
Dilution can be performed using a number of different techniques. One such technique is carried out by reinserting a syringe into the vial containing the reconstituted drug and withdrawing the appropriate amount of drug into the syringe. The contents of the syringe are then injected into a container holding a larger volume of solution commonly termed "diluent." The amount of dilution is a function of the characteristics of the drug, dosage, concentration, and can also be based on a patient's weight or body surface area, as well as other factors. The dilution volume of a drug can range from 0 ml up to a liter, or higher.
One leading method of dilution involves injecting the contents of the syringe containing reconstituted medication into a flexible plastic bag sometimes known as a minibag. The minibag is a single use, sterile package containing an appropriate amount (e.g., 50- or 100- ml's) of diluent. The drug is typically added to the container through an injection port on the minibag.
After the drug has been reconstituted and/or diluted, the pharmacist or technician affixes a preprinted patient-specific label to the bag. A pharmacist verifies the work and signs off on the label. The prepared minibag is then placed into refrigerated storage until delivery to the patient's location.
Despite the verification made by the pharmacist, given the number of IV drugs required by a typical hospital daily, prescription, admixture and delivery errors can still arise. Errors can include, for example: improperly mixed drugs, dosages delivered too early, too late or not all, incorrect dosages ordered by the physician, lost tracking and billing, and costly drug waste. Indeed, a recent report notes that the observed error for compounding I.V. admixtures was 9%. Flynn et al., Observational Study of Accuracy in Compounding I.V. Admixtures at Five Hospitals, American Journal of Health Systems Pharmacia, Vol. 54, Apr. 15, 1997, p. 904. Cohen M R, Davis N M. Confusing and dangerous medical abbreviations that should never be used. Penn Nurse.1991; 46(5):4-5. Cohen M R, Davis N M. Pharmacy label mix-ups. Am Pharm. 1992; NS32(1):26-7. Cohen M R, Davis N M. Minimizing look-alike generic mix-ups. Am Pharm. 1994; NS34(3):22-3. Cohen M R, Davis N M. More look-alike and sound-alike errors. Am Pharm. 1993; NS33(10):32. An incorrect drug delivery can result in increased patient stays and, in some cases, serious injury or death. Studies indicate the average hospital spends approximately $2.8 million annually due to hospital stays extended because of preventable medication errors. Bates D W, The Cost of Adverse Drug Events in Hospitalized Patients, JAMA Jan. 22/29, 1997; Vol.277 No.4, 307-311. The national cost of these extended stays is estimated to exceed $4.2 billion annually. Classen D C, Adverse Drug Events in Hospitalized Patients, JAMA Jan. 22/29, 1997; Vol.277 No.4, 301-306.
In addition to being labor intensive and error-prone, the admixture procedure just described is also wasteful. Often, the reconstituted and diluted drug has a short shelf life. Even with refrigeration, the solution should be discarded after its shelf life has expired, often within a few days after the admixture process. Thus, if a batch is prepared and subsequently not needed, it will likely be wasted.
Furthermore, the use of minibags can lead to fluid overloading of the patient, particularly when multiple drugs are delivered to the patient intravenously. Because multiple drugs usually cannot be diluted simultaneously within the same minibag due to incompatibility potentials, each drug is diluted in its own minibag. This compounds the fluid overloading problem.
Alternatives to the labor-intensive IV admixture process just described have undesirable properties as well. Convenience packaging systems represent an alternative falling into two major categories. The first is premix or frozen premix which is a manufacturer prepackaged drug that is stable when diluted or when diluted and frozen. This method still suffers from the fluid overloading problem discussed earlier. Also, even though the drug stability is extended, there is still a limited shelf life. Additionally, this method suffers from the fact that manufacturers form strategic alliances with specific pharmaceutical companies and package that company's "brand name" drug with their minibag, charging a premium in the process. This prevents a hospital from using the cheaper generic form of the drug should the use of a premixed minibag be desirable.
A second alternative are minibags with vial adapters. A unit dose vial is attached to the minibag's vial adapter and the vial adapter's seal is then broken. The nurse reconstitutes and simultaneously dilutes the drug by moving fluid from the minibag into the vial. This category of minibags suffers from high cost, reduced ability to utilize generic drug substitutes, fluid overloading and the potential for drug waste. In addition, because nurses are not trained as pharmacists, the potential for errors are compounded when the pharmacy does not control the admixture process and nurses perform the so-called "mix and match" on the floor of the hospital.
Referring now to FIG. 1, we illustrate the multiple labor intensive and costly steps which must be carried out for the prior art manual IV admixture process. After a diagnosis 1, an order is written by the medical doctor 2. A pharmacist reviews the order 3, and approves and enters the prescription date 4. Prior to procuring the necessary materials 6, the pharmacist generates a pharmacy pick list of the required items 5. Typically a pharmacy technician then reconstitutes the drug 7 and dilutes the reconstituted medication into a minibag or other container 8. Then the pharmacist checks the work of the technician, initials and places a label on the minibag 9 before the minibag is stored for delivery 10. Steps 3 through 10 represent the pharmacy admixture process 11.
The minibags are thereafter distributed for delivery to the patient. Typically, the minibags are delivered to nursing stations in the general patient area 12 of the hospital. The nurse or other clinician reads the patient's prescription and acquires the medication 13 from the administration station. The clinician checks and verifies that particular medications are correlated with particular patients as per the prescription 14. The medications are then infused into the patient 15. The final step is the logging of the dose delivery and time, denoted as "manual information capture" 16. Steps 12 through 16 represent the administration of medication process 17.
In a effort to avoid the problems associated with the labor-intensive prior art IV admixture process, machine-aided reconstitution systems have been implemented. For example, various embodiments of a reconstitution and delivery system are disclosed in U.S. Pat. No. 4,410,321; U.S. Pat. No. 4,411,662; U.S. Pat. No. 4,432,755; and U.S. Pat. No. 4,458,733. The systems disclosed by these patents, however, require that a number of operations be manually performed by the operator before infusion of the reconstituted medication can be performed. A automated system for reconstituting a drug and delivering the drug intravenously is disclosed in U.S. Pat. No. 5,116,316. Among other potential shortcomings, none of these conventional systems address the problem of preventing medication errors by verifying patient's prescription and drug dosage in the crucial gap between the preparation of the drug through the admixture process and its administration and delivery to a patient.
Whether a drug is manually reconstituted and/or diluted through a manual admixture process or by machine as described in the above patents, the prepared IV drug is delivered into the veins of the patient at bedside. One conventional technique for delivery of the prepared IV drug is for a clinician to use a syringe and simply inject the prepared drug directly into a vein. However, to prevent vein irritation, in some instances it is necessary for the clinician to take several minutes to slowly inject the contents of the syringe into the vein. Moreover, many drugs require larger dilution volumes and longer delivery times than can be practically provided for by manual use of a syringe.
Another conventional technique for delivery of a prepared IV drug is through the use of a syringe pump. For such pumps, a pharmacist selects the appropriate size syringe, fills it, applies a label, attaches a specialized IV set, and delivers this to the clinician. The clinician loads the syringe into a syringe pump and starts the system. The syringe pump delivery system suffers from the costs associated with the labor required by the pharmacist in preparing the syringe and also does not have verification and recording features.
One of the most popular conventional mechanized delivery systems is the peristaltic infusion pump which operates by squeezing the delivery line to force the prepared drug into a vein of the patient. Such a delivery system is illustrated in FIG. 2. The system 32 includes three bags 36, 38, and 39, and a bottle or hard containers 40, each of which contains a fluid to be delivered to the patient. The containers are coupled by flexible fluid flow conduits or tubes 42, 44, 46, and 48, the end of which are coupled to catheters or similar devices for delivering fluid to the patient. Each of the flow lines 42 and 44 includes a conventional peristaltic infusion pump 50 which may be adjusted to deliver a specific volumetric flow to the patient.
Peristaltic pumps exert a great deal of force on the IV line to effectuate pumping. After repeated squeezing, the line loses its round shape, becoming oblong from the pinching force of the peristaltic pump. Such a misshapen line may restrict flow. Thus some peristaltic pumps cannot deliver precise amounts of fluid due to this line distortion phenomenon. Finally, these pumps cannot control air within the line. Although these pumps may have air-in-line sensors at the output of the pump, these pumps cannot detect bubbles at points upstream of the pump outlet and circulate them in a way so as to avoid air being pumped into the pump outlet altogether. The resulting air bubble alarms are a constant nuisance for nursing staff, especially considering that most of the detected bubbles are medically insignificant.
Finally, hospital information systems are frequently less than adequate. Because pharmacists are overworked, they make mistakes and approve orders which they should not have. For example, they may approve: a prescription for a patient with known allergies to the prescribed drug; a prescription to a patient already receiving a different drug which is incompatible with the additional prescribed drug; a drug inappropriate to the patient's diagnosis, an inappropriate amount of a drug when lab values indicate new dosage levels. These mistakes are created by a lack of an integrated information system.
Thus, there is a need for a drug delivery system, which will: automatically reconstitute and dilute medications; is capable of delivering precise amounts of fluids into a patient; can detect air bubbles and recirculate them before they are pumped outside of the pump outlet; can provide a bedside verification that the patient is receiving the correct drug (whether oral, IV, or topical), diluted with the correct diluent, in the correct amount; at the correct time and correct route and will record and document all drugs administered to the patient.